Should spawn with undefined env value be treated as "undefined" string?

[Gerhut]

• Version:

v8.4.0

• Platform:

Darwin 16.7.0 Darwin Kernel Version 16.7.0: Thu Jun 15 17:36:27 PDT 2017; root:xnu-3789.70.16~2/RELEASE_X86_64 x86_64

• Subsystem:

child_process

require('child_process').spawn('/usr/local/bin/node', [
 '-p', 'process.env'
], {
 stdio: 'inherit',
 env: { FOO: undefined }
})

yields

{ FOO: 'undefined', __CF_USER_TEXT_ENCODING: '0x1F5:0x19:0x34' }

should undefined/null environment value be transferred to child process?